Currently sample devices, for example transbronchial needle aspiration (TBNA), include a stylet that is used to assist in sample collection. After puncture with the needle, the stylet inside the needle is pulled back which may help draw tissue into the needle due to creation of reduced pressure.
Other sampling techniques include applying a back and forth technique with the needle to “pack” the tissue into the needle tip.
These methods apply very little vacuum to the tissue and thus, are not reliable tissue extraction techniques.
Another technique uses a vacuum syringe. After puncture, a vacuum is drawn in a syringe and applied to the inside of the needle. This helps draw the tissue up inside. But once the syringe has fully retracted, no more vacuum action can occur. For example, if there is lots of fluid, it will be pulled in first reducing the vacuum to be applied to the (non-fluid) tissue.
Also, tissue may get stuck inside the needle after aspiration. A stylet can be used to push out the tissue or the operator can inject some air using an air source. However, the stylet may damage the sample and attaching air source would make it a more difficult procedure requiring more personnel to successfully complete.